Chemical separations are energy-intensive. About ten percent of the daily energy use by humans is consumed to operate these processes. Despite their large energy demand, chemical separations are essential to the production of food, the purification of drinking water, and the development of therapeutics. As such, a need exists to create energy-efficient and environmentally-responsible sustainable materials and separation processes to produce vital resources that are important to sustaining human life on earth.
Because they do not rely on heat to create a separation, membrane separations avoid the thermodynamic restrictions associated with heat use (i.e., the Carnot efficiency). For example, the success of seawater desalination by reverse osmosis (RO) is a model for the energy savings and sustainability that can be realized by replacing traditional separation processes with membrane separations. At its inception, RO desalination consumed almost three times more energy than equivalent thermal desalination methods, such as multistage flash distillation (MSF). However, over the past forty years, due to fundamental technological advances, the energy demand of seawater RO has fallen dramatically, and it now requires half the energy of MSF. Due to this energy savings, RO is rapidly displacing thermal methods as the preferred desalination technology.
Central to the success of RO desalination was the optimization of the membrane material and membrane structure. Specifically, the transition from asymmetric cellulose acetate membranes to thin-film composite membranes based on polyamide chemistries fueled the success of reverse osmosis. Similar opportunities exist for membrane separations to replace other energy inefficient and environmentally taxing separations processes, such as chromatography and extraction.
Therefore, it is clear that membrane separations have garnered increased attention in recent years because of their ability to bypass the limitations associated with heat use, which is an inherent inefficiency that hinders more traditional, thermally-driven separations. Membranes also are finding application in the purification of thermally-sensitive molecules. At the same time, the purification of dilute solutes is becoming increasingly important to industry. For example, the separation of monoclonal antibodies and other biopharmaceuticals from fermentation broths as well as the isolation of chemicals derived from naturally-occurring resources are emerging areas that rely on robust separation schemes. However, using traditional separations methods to purify these dilute solutes is energy intensive and requires large volumes of solvents, which tax the natural environment and inherently increase the cost of production. As such, the development of membrane processes that can accomplish these separations in a more environmentally-responsible manner while using less energy is an active area of research. Currently, membranes that would allow chromatography or extraction based separation processes to be replaced by membrane separations do not exist.
As such, generating architectures that have monodisperse pore sizes and can attain high fluxes, while adding the ability to tailor pore wall chemistry in order to increase fouling resistance or to perform chemically-selective separations would advance the state-of-the-art in current membrane technologies.